1. Field of the Invention
The present invention relates to a carrier for film carrier type semiconductcr device, and more particularly, to a carrier which holds a film carrier type semiconductor device by engaging the fixing hooks with the sprocket holes of the film carrier.
2. Description of the Prior Art
The fabrication process of a film carrier type semiconductor device (IC) is roughly as in the following. First, a foil of metal such as copper is attached on an insulating base film made of a flexible resin such as polyimide having sprocket holes for conveyance and positioning and a device hole for housing a semiconductor chip, and leads and pads for electrical selection with desired shapes are formed by patterning the metallic foil to constitute a film carrier. Next, a semiconductor chip having metallic protrusions (bumps) formed in advance on the electrode terminals, is prepared, followed by the bonding of the leads of the film carrier and the bumps of the semiconductor chip by means of thermocompression or eutectic welding, completing a film carrier type IC.
A film carrier type IC formed as in the above is subjected to electrical selection or bias test which is carried out through contacts that make contact with the pads of the film carrier tape. In preparation for these types of test the semiconductor chip may be resin sealed by potting of resin for the purpose of assuring the reliability and protecting it from mechanical shocks.
In mounting the film carrier type IC on a printed board, the leads are cut to desired lengths, the semiconductor chip is fixed onto the printed board, then the leads are outer-bonded to the bonding pads formed on the printed board.
For a film carrier type IC, it is possible to perform bonding simultaneously regardless of the number of the leads as described above so that the bonding speed can be made high. Moreover, the IC is of a tape type film carrier so that it is easier to automate the working, and it is small-sized, thin and light-weight compared with other semiconductor devices.
However, the film carrier type IC has a defect that deformation or silvering tend to be generated in the leads formed on its surface because of the flexibility of the base film that constitutes the film carrier. In order to eliminate the defect by mechanically protecting and reinforcing the film carrier type ICs, after cutting the film carrier type ICs into individual pieces, each piece of the cut film carrier type IC is generally mounted on a carrier for IC (referred to simply as a carrier hereinafter) when the IC is subjected to the fabrication processes such as resin sealing and electrical selection, or shipped.
The conventional carrier comprises a square substrate made of resin or the like, an opening formed at the central part of the substrate, a recessed part for holding a film carrier type IC formed in the periphery of the opening, fixing hooks to be inserted to the sprocket holes of the film carrier tape formed in the recessed part placed facing each other with the opening in between, a direction displaying notch formed at one of the corners of the substrate, first holes for letting pins pass through in alignment with the sprocket holes of the film carrier for positioning of the IC, second holes for letting pins pass through, when needed, in alignment with the tooling holes formed in the base film, carrier fixing notches formed in the periphery of the substrate for positioning the carrier, and the like. Among carriers constituted as in the above, there are a type which completely fixes the IC and a type which holds the IC in a state that permits a movement, though only slightly, when a film carrier type IC is mounted on the carrier.
In a carrier of the type where the film carrier type IC is completely fixed with fixing hooks, the positioning of the contacts and the IC pads has to be carried out by means of the carrier fixing notches, so that there is a defect that the positioning accuracy is unsatisfactory. In contrast, in a carrier of the type where the film carrier type IC is held with a margin for movement, a rough alignment of the contacts and the pads is done by means of the carrier fixing notches, and the final positioning can be accomplished by letting the pins go through the sprocket holes on the tooling holes of the film carrier. Consequently, the carrier of the type with a margin for movement is generally being used in widespread manner. It is to be mentioned that the "margin for movement" when a film carrier type with 35 mm width is employed is 0.05 to 0.15 mm.
The fixing hooks provided in the carrier are either provided with a size having the above-mentioned margin so as to be positioned at the approximate centers of the sprocket holes, or given a construction in which the width of the fixing hooks is chosen small and the centers of the fixing hooks are shifted to the outside of the centers of the sprocket holes, that is, so as to prevent an increase in the margin by giving a larger spacing between the opposing fixing holes.
However, the carrier according to the prior art described in the above has a drawback in that when the fixing hooks are inserted to the sprocket holes, the projections formed in their upper parts tend to deform the sprocket holes. In particular, when the width of the fixing hooks is large, the deformation of the sprocket holes by the hooks is large so that they damage the sprocket holes or deform the leads. However, if the width of the fixing hooks is made small as a measure against the sprocket hole, the margin between the fixing hooks and the sprocket holes becomes large, although the deformation of the sprocket holes at the time of insertion of the fixing hooks can be made small, and There may arise cases in which the positioning holes are damaged by the positioning pins at the time of insertion of the pins to the sprocket holes or the tooling holes, making it impossible to obtain an accurate positioning. When the margin is reduced by shifting the fixing hooks toward the outside, the deformation in the sprocket holes at the time of insertion of the fixing hooks becomes large as has been stated in the above.
As a measure against this, in Japanese Patent Laid Open No. 59-72746 and Japanese Patent Laid Open No. 61-90453 have two-piece type carriers which employ two sheets of carriers that have respectively male and female fixing hooks, and are used by sandwiching a film carrier type IC between them. This case, however has a defect in that it leads to an increase in cost because the manufacture of two sheets of carriers must have similar shapes.